In many well applications, downhole fluid samples are collected for analysis. For example, fluid samples may be collected for reservoir characterization. More specifically, fluid samples may be collected to deduce formation fluid properties. The information derived from the formation fluid properties may be used to facilitate the evaluation of reservoir reserves and/or the planning or optimization of reservoir production, among other things.
Fluid sample properties and/or chemical compositions may be better determined from a fluid sample that has been maintained in single phase. Descriptions of methods or apparatus that may be used to maintain a formation fluid in single phase during extraction from a subterranean formation and/or during sample capture may be found, for example, in U.S. Pat. No. 3,351,132 and PCT Patent Application Pub. Nos. 95/18366 and 2008/087156, the disclosures of which are incorporated herein by reference.
Downhole tools have been employed to obtain fluid samples. In certain prior art apparatus, fluids have been extracted from subterranean formations by sealing off a portion of a wall of the well, and reducing the pressure in the sealed off portion to promote fluid flow from the subterranean formations into the downhole tool. Flow conditions, such as the permeability of the fluid through the formation, as well as the pressure, volumetric flow rate, and temperature, may be measured with such apparatus. A description of examples of such downhole tools may be found in “New Wireline Formation Testing Tool With Advanced Sampling Technology” by M. A. Proett, G. N. Gilbert, W. C. Chin, and M. L Monroe, SPE 71317, April 2001, U.S. Pat. No. 7,445,043, and U.S. Patent Application Pub. No. 2008/0066536, the disclosures of which are incorporated herein by reference.